1. Field of the Invention
The present invention relates to a medical bag such as blood bag, transfusion bag or the like to which a tube for charging and discharging a liquid such as blood and transfusion solution into and out of the bag is connected through an outer peripheral seal provided on the tube, as well as to a method of producing the same.
2. Description of the Prior Art
A medical bag such as a blood bag or a transfusion bag is formed by superposing transparent or translucent plastic sheets and then jointing these sheets at their peripheral edges in a sealing manner, with a tube for passing a liquid such as blood or transfusion inserted into the bag through a portion of the jointed edge of the bag so as to provide a communication between the interior and exterior of the tube. In such a medical bag, it is necessary to provide a tight seal between the peripheral surface of the tube and the edges of the sheets contacting the tube. Conventionally, this seal has been achieved by pressing, with the tube placed between the edges of two sheets, the edges of two sheets by a heating mold which has a land of a smooth surface conforming with the shape of the straight tube, so that the edges of the sheets and the tube are pressed tightly to each other thereby to fuse and weld together the material of the sheets and tube to integrate them. According to this method, however, the materials constituting the tube and the sheets are forcibly displaced and flow beyond the predetermined region of seal between the tube and the sheet, to project as burrs into the space in the bag undesirably to making the bag unusable.
Another problem is that, since the tube usually has a larger thickness and, hence, a larger rigidity than the sheets which are generally thin and flexible, the portions of the sheets welded to the free end portion of the tube are thinned excessively thereby becoming weak or permitting the formation of pinholes when the sheets and the tube are welded to each other by the application of high pressure and heat by means of the heating mold having a land of a smooth straight surface.